1. Field of the Invention
The present invention relates to an obstacle data processing system for an unmanned vehicle, adapted for processing data concerning obstacles which may lie in the path of a self-controlled unmanned vehicle so as to enable the vehicle to avert such obstacles.
2. Description of the Related Art
Hitherto, an obstacle data processing system has been known in which non-contact type obstacle sensors are mounted on left and right portions of the front of the vehicle so as to roughly calculate the positions of an obstacle on the basis of the distance between the obstacle and the object as measured by such sensors, and the unmanned vehicle is automatically steered in accordance with the thus calculated position of the obstacle so as to avert the obstacles. An example of such a data processing system is disclosed, for example, in Japanese Patent Laid-Open No. 74905/1984.
FIG. 1 shows a lawn mower as an example of such a self-controlled unmanned vehicle. The vehicle has a chasis DI provided with supersonic sensors 5A and 5B on the front thereof. Both sensors 5A and 5B have an identical construction and are adapted to intermittently transmit supersonic waves to cover predetermined regions and to receive waves reflected by any obstacle A which may lie ahead of the vehicle. The processing system then processes the time between the moment at which the supersonic wave is transmitted and the moment at which the reflected wave is received so as to determine the distance between the obstacle A and the vehicle. The arrangement is such that the areas X.sub.1 and X.sub.2 covered by both sensors 5A and 5B partially overlap each other so that the processing system can determine in which One of three regions A.sub.1, A.sub.2 and A.sub.3 the obstacle exists. FIG. 2 shows a Table showing the relationship between the states of outputs from the sensors 5A and 5B and the position of the obstacle. When the obstacle is sensed by the sensor 5A alone, the processing system judges that the obstacle is on the right side of the vehicle ahead of the same, i.e., in the region A.sub.3, whereas, when the obstacle is sensed by the sensor 5B alone, the system judges that the obstacle is in the left side of the vehicle ahead of the same, i.e., in the region A.sub.1. Thus, when the obstacle is detected by both sensors 5A and 5B simultaneously, the processing system judges that the obstacle resides right ahead of the vehicle.
The processing system then determines only on the basis of such obstacle position data, the angle .theta..sub.1, .theta..sub.2 and .theta..sub.3, as shown in Table in FIG. 2.
In another known system, the obstacle is detected through scanning by a TV camera or a supersonic range finder having a narrow directivity so as to precisely determine the position of the obstacle three-dimensionally. In some advanced systems, data concerning complicated configuration of the obstacle is extracted in order to recognize or identify the object.
The system proposed in the above-mentioned Japanese Patent Laid-Open No. 74905/1984, however, suffers from the following disadvantage. Namely, the data concerning the position of the obstacle is utilized only in the control of simple averting action such as stopping or simple steering operation each time an obstacle is detected. Namely, there is no means for storing and accumulating such position data in such a manner as to grasp the distribution of many obstacles nor for utilizing the data concerning such a distribution in averting the obstacles. In addition, the accuracy of finding of the position is not so high so that repetition of simple try-and-error is necessary each time an obstacle is detected.
Other known systems mentioned above necessitate large-scale apparatus because they employ a TV camera or a scanning supersonic range finder of narrow directivity not only for the purpose of detecting an obstacle but also for conducting various operations such as extraction of three-dimensional dimensional position of the obstacle, recognition of the complicated configuration of the obstacle and the identification of the obstacle. In addition, these operations are generally time-consuming and the data acquired through such operations may include data which are not directly utilized in the averting action.
Thus, the conventional obstacle position data processing system does not incorporate any function which would grasp the pattern of distribution of many obstacles through accumulation of the obstacle position data, so that the vehicle can conduct only a simple averting operation such as stopping or a predetermined steering. In addition, in some known systems, the data processing is impractically low because the acquired data contain those data which are not directly utilized in the averting operation.
Under these circumstances, the present inventors have made an intense study and found that, though the position data obtained each time an obstacle is detected is limited, an accumulation of such obstacle position data can form a data concerning distribution of a plurality of obstacles which is necessary and enough for enabling the vehicle to avert such obstacles, whereby major problems of the prior art are overcome.